A method for installing siding panels to a building includes providing a fo am backing board having alignment ribs on a front surface and a drainage grid o n a back surface and then establishing a reference line at a lower end of the buildin g for aligning a lower edge of a first backing board and tacking thereon. Tabs and slots along vertical edges of the foam backing board align and secure adjacent backing boards to each other. A siding panel is butted against one of the lower alignment ribs and secured thereto. Another siding panel is butted against and secured to a n adjacent alignment rib to form a shadow line between the adjacent siding panels on th e building.
